This invention relates to an improved docking mechanism for a semiconductor tester.
A semiconductor tester operates in conjunction with another machine, such as a wafer prober, a device handler or a calibration station. In each case, it is necessary to bring a test head of the semiconductor tester to a predetermined position with respect to the other machine (which is referred to hereinafter simply as the machine) and firmly secure, or dock, the test head to the machine employing a mechanical interface which includes a docking plate attached to the test head and docking bars or gussets attached to the machine. Docking is accomplished by lining up guide pins on the docking plate with guide pin sockets in the docking bars. When the guide pins are aligned with the guide pin sockets, cam followers carried by the docking bars are positioned relative to the entrances to respective cam slots in cam blocks that are carried by the docking plate so that on movement of the test head toward the machine along a docking axis parallel to the guide pins, the cam followers will enter the entrances to the cam slots. When the cam followers are properly positioned in the entrances to the cam slots, the cam blocks are displaced relative to the docking plate and the docking bars. Cooperation of the cam blocks with the cam followers pulls the docking plate and the docking bars firmly together.
It is necessary that the test head be accurately positioned relative to the machine, both with respect to planarity and with respect to translation, with the cam followers properly received in the entrances to the cam slots, before the cam blocks are displaced for docking the test head to the machine. Otherwise, the cam blocks may collide with the cam followers, resulting in damage to the mechanism for driving the cam blocks. However, it can be difficult to determine whether the test head is properly positioned relative to the machine, and, if it is not, the nature of the error in positioning because it is difficult to view the cam followers and the cam slots when the docking plate is close to the machine.
In one known arrangement, the cam blocks are moved linearly along parallel paths, parallel to the docking bars, and movement of the cam blocks is coordinated by virtue of the fact that they are connected by a cable which is wrapped around pulleys attached to the docking plate. Movement of the cam blocks is brought about by turning one of the pulleys.
This known type of docking mechanism is subject to disadvantage because it does not include a mechanism for preventing movement of the cam blocks in the event that the cam followers are not properly received in the entrances to the cam slots.
According to a first aspect of the present invention there is provided a docking mechanism for docking a test head to a machine, wherein the test head includes a first docking structure and cam members which are moveable with respect to the first docking structure between a first position and a second position and the machine includes a second docking structure and cam followers for engaging cam slots in the cam members when the first docking structure is in a predetermined position with respect to the second docking structure and the cam members are in the first position, so that when the cam members are moved to the second position the first and second docking structures are drawn together along a docking axis, the docking mechanism comprising at least two sensors carried by one of the first and second docking structures and spaced apart from one another, the sensors cooperating with the other of the first and second docking structures and being in a first state when the first docking structure is not engaged with the second docking structure and the first docking structure is being brought towards, but has not attained said predetermined position, and being in a second state when the first docking structure attains said predetermined position.
According to a second aspect of the present invention there is provided a docking mechanism for docking a test head having a docking plate and cam members which are moveable with respect to the docking plate between a first position and a second position to a machine having a docking fixture including cam followers for engaging cam slots in the cam members when the docking plate is in a predetermined position with respect to the docking fixture and the cam members are in the first position, so that when the cam members are moved to the second position the docking plate and the docking fixture are drawn together along a docking axis, the docking mechanism comprising at least two sensors carried by the docking plate and spaced apart from one another, the sensors cooperating with the docking fixture and being in a first state when the docking plate is not engaged with the docking fixture and the docking plate is being brought towards, but has not attained said predetermined position, and being in a second state when the docking plate attains said predetermined position.
According to a third aspect of the present invention there is provided a docking mechanism for docking a test head of a semiconductor tester to a machine, wherein the test head has a first docking structure and latch members which are moveable with respect to the first docking structure between a first position and a second position and the machine has a second docking structure including engagement elements for engagement by the latch members when the first docking structure is in a predetermined position with respect to the second docking structure and the latch members are in the first position, so that when the latch members are moved to the second position the first docking structure is drawn towards the second docking structure along a docking axis, the docking mechanism comprising at least two sensors, each sensor being carried by one of the first and second docking structures and cooperating with the other of the first and second docking structures so that the two sensors are sensitive to planarity and translation of the test head relative to the machine, the sensors being in a first state when the first docking structure is being brought towards, but has not attained said predetermined position, and being in a second state when the first docking structure attains said predetermined position.